EP-B1-0 131 127 discloses a process for producing crosslinking components for use in paint binders crosslinkable through transesterification and/or transamidation, characterized in that compounds of the structure - EQU X--CH.sub.2 --COOR,
wherein X is --COOR, --CN or COCH.sub.3 and R is an alkyl radical with from 1 to 8 carbon atoms, preferably the diesters of malonic acid with alkanols with from 1 to 4 carbon atoms, are reacted with a carbonyl compound, preferably formaldehyde and in particular paraformaldehyde, with separation of water in the sense of a KNOEVENAGEL-reaction, and the resulting alpha-disubstituted alkylidene compound is polymerized to an oligomeric or polymeric compound with a molecular weight of between 300 and 6000.